Description of Business and Significant Accounting Policies - Revenue Recognition (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Description Of Business And Significant Accounting Policies [Line Items]
Deferred commissions balance, beginning of period	$ 17,331,000	$ 18,408,000
Deferral of commissions earned	18,333,000	15,312,000
Recognition of commission expense	(17,364,000)	(16,240,000)
Impairment of deferred commissions	(398,000)	(149,000)
Deferred commissions balance, end of period	17,902,000	17,331,000
Other assets
Description Of Business And Significant Accounting Policies [Line Items]
Unbilled receivables, noncurrent	795,000	592,000
Unbilled
Description Of Business And Significant Accounting Policies [Line Items]
Accounts receivable	$ 2,043,000	$ 1,382,000
Minimum
Description Of Business And Significant Accounting Policies [Line Items]
Payment terms	30 days
Maximum
Description Of Business And Significant Accounting Policies [Line Items]
Payment terms	60 days
Total revenue | Product | Appliance | Maximum
Description Of Business And Significant Accounting Policies [Line Items]
Concentration risk, percentage	2.00%